1. Field of the Invention
This invention relates to a safety device for a pneumatic tool such as an air hammer or an air grinder, the operation of which is initiated and terminated by means of an operation lever.
2. Description of the Related Art
Unexamined Japanese Utility Model Registration Application Publication Sho No. 62-21420 discloses a safety device for a pneumatic tool operated by a lever. FIGS. 1 and 2 show this conventional safety device. An operation lever 1 has one end pivoted to the rear end portion of the pneumatic tool 2 by means of a pin 3 and is pushed upward to an inclined state by means of a spring 4, as shown in FIG. 1. When a valve stem 13 is lowered by the operation lever 1, the pneumatic tool 2 is operated. A slide plate 5 and a stop plate 6 are fixed together by means of a screw 11 so that they contact with and are slidable on the upper and lower faces of the operation lever 1, respectively. When the pneumatic tool 2 is not being operated, the distal end 15 of the stop plate 6 abuts against a safety pin 14 fixed to the main body of the pneumatic tool 2 by the urging force of a spring 12 received in a recess 9 formed in the operation lever 1 so that the operation lever 1 is prevented by means of the safety pin 14 from being lowered. If depressed when the pneumatic tool 2 is in the unoperated state, the lever 1 will not rotate downward around the pin 3. Therefore, the safety of the pneumatic tool 2 is ensured when it is not being operated.
As a push portion 8 is moved rightward, as shown in FIG. 1, against the biasing force of the spring 12 by the operator's finger, the stop plate 6 is displaced to the position where a pin hole A formed in the stop plate 6 coincides with a pin hole B formed in the operation lever 1. When the lever 1 is rotated downward in this state, the safety pin 14 is inserted in the holes A and B, and the operation lever 1, without being obstructed in its operation by any other members, pushes the valve stem 13. In other words, the operation of the pneumatic tool 2 can start only when the operation lever 1 occupies this position.
However, in the case of the conventional safety device, the slide plate 5 and the stop plate 6 slidably mounted on the upper and lower faces of the operation lever 1 and the spring 12 housed therein result in the operation lever 1 being very thick, making it somewhat difficult to operate. Further, since the slide plate 5 as well as the push portion 8 thereof projects from the upper face of the operation lever 1, the operator's palm may sometimes hit against the projecting portion of the slide plate 5, including prickly sensation in his palm when the operation lever 1 is pushed. Still further, the safety device requires many parts including the safety pin 14, rendering its structure complicated.